Exactly. I think Cruyff would be the best addition to the other 3 protagonists.
He would perfectly control distances and adapt to the movements of Pelé and Ronaldo. He had great tactical intelligence and would be capable of systematically molding this star-studded front four into a cohesive unit.
His ability to create and exploit space harmonizes perfectly with the positional freedom of Messi and the other strikers who leave their positions (Cristiano would play that LW-CF-hybrid where he can use his finishing, especially his heading ability, to the maximum). Cruyff, along with Messi and Xavi, would be the playmaker, coordinating the actions of individual players, but he could also push forward himself when necessary. In attack, this system focuses heavily on flexibility and fluid football, in which Pelé, Messi and Cruyff in particular frequently exchange positions.
Based on his sheer individual ability Maradona has to be included in an all time XI. But if he and Messi were to play directly next to each other on the field (right wing and number 10), I think they would be restricting each other's freedom. Ultimately, they cover the same areas and their playing styles are generally too similar.